1. Field of the Invention
This invention relates to a liquid crystal display module, and more particularly to a liquid crystal display module that prevents physical noise caused by friction between a support main and a light guide plate.
2. Description of the Related Art
Generally, a liquid crystal display (LCD) includes a liquid crystal display module, driving circuitry for driving the liquid crystal display module, and a case.
The liquid crystal display module consists of a liquid crystal display panel having liquid crystal cells arranged in a matrix between two glass substrates, and a backlight unit which irradiates light onto the liquid crystal display panel. The liquid crystal display module is arranged with optical sheets which vertically raise light traveling from the backlight unit toward the liquid crystal display panel.
However, the aforementioned liquid crystal display panel, backlight unit and optical sheets must engage with each other in an integral shape to prevent light loss and have protection from a damage caused by an external impact. Thus, a case for the LCD enclosing the back light unit and the optical sheets including the edge of the liquid crystal display panel is provided. The above-mentioned LCD is mounted in a portable information processing device such as a notebook personal computer to thereby be used as a display device.
Referring to FIG. 1 and FIG. 2, a related art liquid crystal display module includes a support main 14, a backlight unit and a liquid crystal display panel 6 disposed at an inside of the support main 14, and a case top 2 for securing the liquid crystal display panel 6 and the support main 14.
The liquid crystal display panel 6 comprises an upper glass substrate 6a and a lower glass substrate 6b. Liquid crystal cells are arranged in an active matrix type between the upper glass substrate 6a and the lower glass substrate 6b, and are provided with thin film transistors which switch video signals. The liquid crystal display panel 6 changes a refractive index of each liquid crystal cell in accordance with video signals thereby displaying a picture corresponding to the video signals. An upper polarizing sheet 4a is attached to an upper side of the upper glass substrate 6a while a lower polarizing sheet 4b is attached to a rear side of the lower glass substrate 6b. 
A tape carrier package (not shown) mounted with a driver integrated circuit that applies a driving signal to the thin film transistor is attached to the lower substrate 6b of the liquid crystal display panel 6.
The support main 14 is molded and an inner side wall surface thereof is molded into a step coverage face. The step coverage face of the support main 14 is mounted with a back light unit and the liquid crystal display panel 6 is disposed thereon.
The backlight unit includes a lamp 21, a lamp housing 23, a reflective sheet 12, a light guide plate 10 and optical sheets 8.
The lamp 21 includes a cold cathode fluorescent lamp. A light generated from the lamp 21 is incident, via an incidence face at the side of the light guide plate 10, to the light guide plate 10.
The lamp housing 23 has a reflective face at its inner side which reflects light from the lamp 21 into the incidence face of the light guide plate 10.
The reflective sheet 12 is positioned at a rear side of the light guide plate 10 to re-reflect an incident light, via the rear side of the light guide plate 10, to the light guide plate 10, thereby reducing light loss.
An incidence face of light guide plate 10 engages with the lamp housing 23, and a second portion of the light guide plate 10 secures to the support main 14. The light guide plate 10 converts a line light input from the lamp 21 into a plane light thereby guiding the light into the liquid crystal display panel 6. Simultaneously, the reflective sheet 12 reflects light traveling into the lower side of the light guide plate 10 toward the liquid crystal display panel 6. A light output from the light guide plate 10 with the lamp 21 is incident, via a plurality of optical sheets 8, to the liquid crystal display panel 6.
The optical sheets 8 allow light input from the light guide plate 10 to travel vertically into the liquid crystal display panel 6. To further illustrate, the optical sheets 8 change a light path perpendicularly to the liquid crystal display panel 6. The optical sheets 8 comprise first and second prism sheets between first and second diffusing sheets.
The case top 2 has a square band shape including a plane part bent perpendicularly and a side part bent perpendicularly. The top case 2 encloses an edge of the liquid crystal display panel 6 and the support main 14.
Upon assembling the liquid crystal display module, the support main 14 and the light guide plate 10 are provided with a plurality of engaging parts 50 for engagement between the support main 14 and the light guide plate 10 as shown in FIG. 3.
More specifically, each engaging part 50 comprises a square hole 20 at a side of the support main 14, and a protrusion 25 protruding from a side of the light guide plate 10. The protrusion 25 at the light guide plate 10 protrudes, by a desired length, from each side surface and a lower surface of the light guide plate 10 as shown in FIG. 4. Each square hole at the support main 14 is formed a certain size at a portion corresponding to the protrusion 25 provided at the light guide plate 10 as shown in FIG. 4 such that the protrusion 25 can be inserted into each square hole.
As described above, in a related art liquid crystal display module, the protrusion 25 of the light guide plate 10 is inserted into the square hole 20 of the support main 14 thereby securing the light guide plate 10 to the support main 14. As shown in FIG. 5, each corner of the light guide plate 10 is opposed to each corner 30 of the square hole 20 of the support main 14 in a diagonal direction. The support main 14 is formed from a relatively lightweight mold product which reduces a weight of the liquid crystal display module. Thus, if an external force is applied to one side of the related art liquid crystal display module, twist occurs at the liquid crystal display module. In addition, the support main 14 twists into one side thereof by an external force applied to one side of the support main 14 as shown in FIG. 6. Accordingly, friction occurs between the square hole 20 of the twisted support main 14 and the light guide plate 10, thereby causing noise. More specifically, when the support main 14 twists, a lower surface of the square hole 20 contacts a corner portion 38 of an upper side of the light guide plate 10. The friction generates noise at the corner portion 38 where the support main 14 contacts the light guide plate 10.
Furthermore, in a related art liquid crystal display module, friction between the square hole 20 of the support main 14 and the protrusion 25 of the light guide plate 25 caused by twisting of the support main 14 generates an alien substance. If the alien substance lodges between the light guide plate 10 and the optical sheets 8, light passing through the light guide plate 10 may shut off thereby causing a black spot at a position of the liquid crystal display panel 6 corresponding to the alien substance.